1. Field of the Invention
The present invention relates to packaging material for flowable food containers. Specifically, the present invention relates to a laminate composed of at least one layer of a corrugated packaging material for a container for flowable materials.
2. Description of the Related Art
Containers for flowable food products are available in various forms. One form is the commonly recognizable gabletop carton such as the TETRA REX.RTM. carton available from Tetra Pak, Inc. of Chicago, Ill. Another type of container is the ubiquitous TETRA BRIK.RTM. parallelepiped container also available from Tetra Pak, Inc. of Chicago, Ill. The gabletop carton includes four side panels which are finished, at the top, with a peaked, gable-like configuration while the parallelepiped container is formed from a web of material and has four sides and a substantially flat top and bottom. Such containers are used for packaging and storing liquid foods such as milk, juice and the like, as well as other, consumer liquid products such as laundry detergent. Such containers are also used for storing dried, powdered and granulated good, such as dried soups. Such containers are also known for use in storing medicinal goods such as powdered or granulated Epsom salts.
Traditionally, such gabletop cartons are formed from "blanks" which are formed or erected and transported into a filling apparatus in which the carton is filled and the top or gable portion folded and sealed. The blanks are shipped and stored unformed or flat. The cartons are generally erected within the filling machine. As mentioned above, parallelepiped containers are fabricated on a vertical form, fill and seal packaging machine from a web of material.
In a common arrangement for liquid packaging and storage, the packaging material is formed from a laminated structure. One known laminate includes a fiberboard substrate having a layer or a coating of a polymeric material, such as low density polyethylene (LDPE) on both sides of the substrate. The "sides" of the substrate are the inside and outside surfaces of the container is completely formed.
The polymeric layers provide a measure of liquid impermeability to the material, thus providing a substantially "leak resistant" container, with the inner polymeric layer preventing leakage from the container outward, and the outer polymeric layer retarding moisture or humidity transfer from the environs inward. The laminated structure also reduces wicking of the material, which is absorption of liquid by the container material, and subsequent mass transfer, of the liquid from the site of absorption.
The laminate may also include a barrier layer adjacent to the substrate, between the substrate and the inner polymeric layer. The barrier layer enhances gas impermeability of the carton which facilitates retaining the container contents fresh. The barrier layer can be positioned directly on the substrate. Alternately, and preferably, the laminate can include a polymeric layer between the barrier layer and the substrate as well as a polymeric layer over the barrier. In this configuration, the polymeric layer that is disposed between the barrier and the substrate can serve to adhere the barrier and substrate to one another. Such barrier layers are used, typically, in cartons for storing fruit juice and the like.
A major cost in the manufacture of such containers is the cost of the paper materials, which correlates to paper grammage for each container. Paper products are often measured in "grammage", which is the weight of the board in grams per square meter, (gms/m.sup.2). As such, increased "grammage" of materials generally correlates to increased cost. Any reduction in paper grammage generally brings about a savings in the cost of the container. However, relatively lighter weight materials, i.e., lower grammage materials, generally have less strength than materials having a higher grammage. As such, a balance must be made between cost reduction and strength.
Accordingly, there continues to be a need for a lighter weight material for the manufacture of paperboard and paperboard-like Paper products are often measured in "grammage", which is the weight of the board in grams per square meter (gms/m.sup.2). As such, increased "grammage" of materials generally correlates to increased cost. Such a material and carton configuration provides strength and durability in a reduced cost package for packaging and storing solid, viscous and liquid goods.